Abstract
A combined experimental and theoretical study of the band gap of AlInN is presented, which confirms the breakdown of the virtual crystal approximation (VCA) for the conduction and valence band edges. Composition-dependent bowing parameters for these quantities are extracted. Additionally, composition-dependent band offsets for GaN/AlInN systems are provided. We show that local strain and built-in fields affect the band edges significantly, leading to optical polarization switching at a much lower In composition than expected from a VCA approach.